Air conditioning system and method for controlling the same

ABSTRACT

The present invention relates to air conditioning systems, and more particularly, to an air conditioning system which can control a refrigerant flow rate to a heat exchanger exchanging heat with room air to be optimum; and a method for controlling the same. The air conditioning system includes an outdoor heat exchange part including a compressor for compressing refrigerant, an outdoor heat exchanger for making the refrigerant to heat exchange with outdoor air, and an expansion device for expanding the refrigerant, an indoor heat exchange part including a pump for making refrigerant in a flow path independent from the outdoor heat exchange part to flow, at least one indoor heat exchanger for making the refrigerant heat exchange with room air, and a flow rate control device for controlling a flow rate of the refrigerant, and a hybrid heat exchange part for making the outdoor heat exchange part and the indoor heat exchange part, which are independent from each other, to heat exchange with each other. According to this, the air conditioning system can be installed on a multistory building without limitation of a height of the building as far as a capacity of the pump permits. Moreover, even if a refrigerant pipe is long, the air conditioning system is applicable even to a system with a refrigerant pipe line longer than the related art as far as the capacity of the pump permits, and fine control of a room air temperature is possible.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Application No.P2004-96315 filed on Nov. 23, 2004, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to air conditioning systems, and moreparticularly, to an air conditioning system which can control arefrigerant flow rate to a heat exchanger exchanging heat with room airto be optimum; and a method for controlling the same.

2. Discussion of the Related Art

In general, the air conditioning system cools or heats a room bycompressing, condensing, expanding, and evaporating refrigerant. Ingeneral, the air conditioning system is provided with a compressor, anindoor heat exchanger, an expansion device, and an outdoor heatexchanger.

In the air conditioning systems, there are a cooling system in which arefrigerating cycle is operated only in one direction, to supply onlycold air to the room, and a heating/cooling system in which therefrigerating cycle is operated in two directions selectively, to supplycold air or warm air to the room.

Moreover, in the air conditioning systems, depending on a number ofindoor units connected thereto, there are single air conditioningsystems in each of which one indoor unit is connected to one outdoorunit, and multiple air conditioning systems in each of which a pluralityof indoor units are connected to one outdoor unit.

The air conditioning system uses the compressor as a driving source formaking the refrigerant to flow, and oil for lubricating the compressor.

However, if a height difference or a distance between the indoor heatexchanger, and the outdoor heat exchanger is great significantly, sincethe related art air conditioning system has a poor oil recovery rate, tofail in supply of an adequate rate of oil to the compressor, which isliable to result in damage to the compressor, development of an airconditioning system that can solve such a problem has been required.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an air conditioningsystem and a method for controlling the same that substantially obviatesone or more problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a an air conditioningsystem and a method for controlling the same, which is applicable evento a case a height difference or a distance between an indoor heatexchanger, and an outdoor heat exchanger is great significantly.

Another object of the present invention is to provide an airconditioning system and a method for controlling the same, which enablesa fine control of a room temperature.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, anair conditioning system includes an outdoor heat exchange part includinga compressor for compressing refrigerant, an outdoor heat exchanger formaking the refrigerant to heat exchange with outdoor air, and anexpansion device for expanding the refrigerant, an indoor heat exchangepart including a pump for making refrigerant in a flow path independentfrom the outdoor heat exchange part to flow, a indoor heat exchanger formaking the refrigerant heat exchange with room air, and a flow ratecontrol device for controlling a flow rate of the refrigerant, and ahybrid heat exchange part for making the outdoor heat exchange part andthe indoor heat exchange part, which are independent from each other, toheat exchange with each other.

The flow rate control device may include a temperature sensor formeasuring temperatures of refrigerant flowing in the indoor heatexchanger, a controller for determining a degree of superheat orsubcooling of the refrigerant with the temperatures measured at thetemperature sensor, and a flow rate control valve for controlling arefrigerant flow rate to the indoor heat exchanger according to thedetermination of the controller.

The flow rate control valve may be mounted on a refrigerant inlet end ofthe indoor heat exchanger.

The flow rate control valve may be mounted on a refrigerant outlet endof the indoor heat exchanger.

The temperature sensors are mounted on the refrigerant inlet end, therefrigerant outlet end, and a predetermined portion between therefrigerant inlet end and the refrigerant outlet end of the indoor heatexchanger. Preferably, the predetermined portion between the refrigerantinlet end and the refrigerant outlet end of the indoor heat exchanger isa section in which the refrigerant flowing in the indoor heat exchangeris in a saturated state.

In the meantime, in another aspect of the present invention, a methodfor controlling an air conditioning system includes the steps of settingan ideal degree of superheat, and an ideal degree of subcooling at acontroller, comparing the degree of superheat or subcooling set thuswith a degree of superheat or subcooling measured thus, and controllinga flow rate of refrigerant flowing in an indoor heat exchanger accordingto a result of the step of comparing the degree of superheat orsubcooling set thus with a degree of or subcooling measured thus.

The degree of superheat or subcooling is a difference between atemperature of the refrigerant at the refrigerant outlet of the indoorheat exchanger and a saturation temperature of the refrigerant flowingin the indoor heat exchanger.

The step of controlling a flow rate of refrigerant flowing in an indoorheat exchanger includes the steps of increasing the flow rate of therefrigerant flowing in the indoor heat exchanger if the degree ofsuperheat measured is higher than the degree of superheat set, anddecreasing the flow rate of the refrigerant flowing in the indoor heatexchanger if the degree of superheat measured is lower than the degreeof superheat set.

The step of controlling a flow rate of refrigerant flowing in an indoorheat exchanger includes the steps of increasing the flow rate of therefrigerant flowing in the indoor heat exchanger if the degree ofsubcooling measured is higher than the degree of subcooling set, anddecreasing the flow rate of the refrigerant flowing in the indoor heatexchanger if the degree of subcooling measured is lower than the degreeof subcooling set.

In another aspect of the present invention, an air conditioning systemincludes at least one first heat exchanger for heat exchange with roomair, a second heat exchanger for transferring heat from the first heatexchanger to an outside of a refrigerant flow path having the first heatexchanger mounted therein, a pump for circulating the refrigerant to thefirst heat exchanger and the second heat exchanger, a third heatexchanger in a flow path independent both from the first heat exchangerand the second heat exchanger for heat exchange with the second heatexchanger, a fourth heat exchanger for transferring heat from the thirdheat exchanger to outdoor air, a compressor for compressing therefrigerant and circulating the refrigerant to the third heat exchangerand the fourth heat exchanger, a plurality of temperature sensors formeasuring temperatures of the refrigerant flowing in the first heatexchanger, at least one flow rate control valve for controlling a flowrate of the refrigerant flowing in the first heat exchanger according totemperatures measured at the temperature sensors.

The temperature sensors are provided at a refrigerant inlet end and arefrigerant outlet end of the first heat exchanger, and at apredetermined portion between the refrigerant inlet end and therefrigerant outlet end, respectively. The temperature sensor provided ata predetermined portion between the refrigerant inlet end and therefrigerant outlet end measures a saturation temperature of therefrigerant flowing in the first heat exchanger.

The flow rate control valves are provided to a refrigerant inlet end anda refrigerant outlet end of the indoor heat exchanger. At the time ofcontrolling a refrigerant flow rate, an opening of the flow rate controlvalve at the refrigerant inlet end of the first heat exchanger isadjusted, and an opening of the flow rate control valve at therefrigerant outlet end is opened to the maximum.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings;

FIG. 1 illustrates a diagram of an air conditioning system in accordancewith a preferred embodiment of the present invention, schematically;

FIG. 2 illustrates a diagram of an indoor heat exchange part in the airconditioning system in FIG. 1, schematically;

FIG. 3 illustrates a flow chart showing the steps of a method forcontrolling an air conditioning system in accordance with a preferredembodiment of the present invention;

FIG. 4 illustrates a P-h diagram showing a state change of refrigerantin cooling operation of the air conditioning system in FIG. 1; and

FIG. 5 illustrates a P-h diagram showing a state change of refrigerantin heating operation of the air conditioning system in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIGS. 1 and 2 illustrate diagrams each showing an air conditioningsystem in accordance with a preferred embodiment of the presentinvention.

Referring to FIGS. 1 and 2, the air conditioning system includes anindoor heat exchange part 10 for heat exchange with room air, an outdoorheat exchange part 20 for heat exchange with outdoor air, and a hybridheat exchanger 30 for making refrigerant in the indoor heat exchangepart 10 and refrigerant in the outdoor heat exchange part 20 to heatexchange with each other.

The indoor heat exchange part 10 includes a first heat exchanger 14 forheat exchange with the room air, a pump 12 for circulating therefrigerant to the first heat exchanger 14, and a flow rate controldevice for controlling a flow rate of the refrigerant to the first heatexchanger 14.

The outdoor heat exchange part 20 has a refrigerant flow pathindependent from the indoor heat exchange part 10, and includes a fourthheat exchanger 24 for making the refrigerant to heat exchange withoutdoor air, and a compressor 22 for compressing, and circulating therefrigerant to the fourth heat exchanger 24.

The outdoor heat exchange part 20 includes an expansion device 28 forexpanding the refrigerant to drop a pressure of the refrigerant, and aflow controller 23 for controlling a flow direction of the refrigerant,additionally.

In the meantime, the outdoor heat exchange part 20 may have manyvariations as far as the part can transfer heat to the refrigerant inthe indoor heat exchange part 10. As an example, the part may use warmwater or waste heat as a heat source.

The hybrid heat exchange part 30 is configured such that the indoor heatexchange part 10 and the outdoor heat exchange part 20 havingrefrigerant flow paths independent from each other can heat exchangewith each other, without mix of the refrigerant between the indoor heatexchange part 10 and the outdoor heat exchange part 20.

In order to enable the indoor heat exchanger 10 and the outdoor heatexchanger 20 make heat exchange with each other, the hybrid heatexchange part 30 includes a second heat exchanger 16 in a flow path ofthe indoor heat exchange part 10, and a third heat exchanger 26 in aflow path of the outdoor heat exchange part 20 for heat exchange withthe second heat exchanger 16.

That is, the second heat exchanger 16 exchanges heat with the third heatexchanger 26 so that the indoor heat exchange part 10 and the outdoorheat exchange part 20 make heat exchange.

Moreover, the second heat exchanger 16 forms a refrigerant circulatingflow path as a portion of the indoor heat exchange part 10, and thethird heat exchanger 26 forms a refrigerant circulating flow path as aportion of the outdoor heat exchange part 20.

That is, the outdoor heat exchange part 20 forms a refrigerant flow pathwith the third heat exchanger 26, the fourth heat exchanger 24, thecompressor 22, and the expansion device 28, and the indoor heat exchangepart 10 forms a refrigerant flow path with the first heat exchanger 14,the second heat exchanger 16, the pump 12, and a flow rate controldevice.

The second heat exchanger 16 and the third heat exchanger 26 may havemany variations. That is, the second heat exchanger 16 and the thirdheat exchanger 26 may be constructed of heat dissipation plates, orrefrigerant tubes.

The hybrid heat exchange part 30 is configured to enable the second heatexchanger 16, and the third heat exchanger 26 in the outdoor heatexchange part to make thermal contact with each other.

For an example, the hybrid heat exchange part 30 may be constructed of astack of a plurality of plate type heat conductive fins having thesecond heat exchanger 16 and the third heat exchanger 26 placedtherebetween so as to be thermally in contact with each other.

Or alternatively, the hybrid heat exchange part 30 may has a structurein which the second heat exchanger and the third heat exchanger heatexchange with each other through a heat conductive fluid. Or, the secondheat exchanger 16 and the third heat exchanger 26 are configured to havea form of a double tube.

In the meantime, the indoor heat exchange part 10 will be described inmore detail.

As described before, the indoor heat exchange part 10 has a flow pathindependent from the outdoor heat exchange part 20, and includes a firstheat exchanger 14, a pump 12, a flow rate control device, and a secondheat exchanger 16 of the hybrid heat exchange part 30.

The indoor heat exchange part 10 has a pump 12 instead of a compressoras a driving source for making the refrigerant to flow, and has noseparate expansion device for expanding the refrigerant. Owing to this,the indoor heat exchange part 10 requires no oil for operation of thecompressor, and consequently, no operation for recovery of therefrigerant is required.

It is preferable that the pump 12 includes a pumping motor (not shown)and an impeller (not shown). Moreover, it is preferable that liquidrefrigerant is supplied to the pump 12, for which, though not shown, aseparate refrigerant storage tank may be provided between the hybridheat exchange part 30 and the pump 12, for supplying refrigerant to thepump 12.

It is preferable that an inverter motor is employed as the pumping motorfor controlling a rotation speed of the motor, to control a flow rate ofthe refrigerant. Of course, a constant speed motor having a constantrotation speed may be used.

In general, the first heat exchanger 14 is mounted in an indoor unit 15installed in a room which requires cooling/heating. That is, the firstheat exchanger 14 is an indoor heat exchanger for heat exchange withroom air to cool or heat the room.

There may be a plurality of indoor units 15 installed in a room ifrequired, and according to this, a plurality of indoor heat exchangers14 may be mounted thereon.

The flow rate control device includes a plurality of temperature sensors17 a, 17 b, and 17 c for measuring temperatures of the refrigerantflowing through the indoor heat exchanger 14, a controller (not shown)for determining a degree of superheat or subcooling of the refrigerantin the indoor heat exchanger 14 with reference to the temperaturesmeasured at the temperature sensors 17 a, 17 b, and 17 c, and flow ratecontrol valves 13 a, and 13 b for controlling a flow rate of therefrigerant to the indoor heat exchanger 14 according to thedetermination of the controller.

It is preferable that the flow rate control valve 13 a, and 13 b aresolenoid valves each for controlling an opening of a flow passage withan electromagnetic force. Of course, there can be a variety of the flowrate control valves 13 a, and 13 b as far as the valve can control theopening of the flow passage.

Moreover, though it is preferable that the flow rate control valve 13 a,and 13 b are mounted on opposite ends of the indoor heat exchanger 14into which the refrigerant flows in/out, the mounting positions of theflow rate control valve 13 a, and 13 b are not limited to this, but theflow rate control valve 13 a, and 13 b may be mounted only one of theopposite ends.

Mounting positions of the temperature sensors will be described withreference to FIG. 2.

It is preferable that the temperature sensors 17 a, 17 b, and 17 c aremounted on an inlet 17 a through which the refrigerant is introducedinto the indoor heat exchanger 14, an outlet 17 b through which therefrigerant is discharged from the indoor heat exchanger 14, and apredetermined portion 17 c between the inlet 17 a, and the outlet 17 b,respectively.

That is, at least three temperature sensors 17 a, 17 b, and 17 c aremounted on every indoor heat exchanger 14 mounted on the indoor unit 15.

Of the three temperature sensors 17 a, 17 b, and 17 c, it is preferablethat the temperature sensor 17 c mounted on the predetermined portionbetween the inlet 17 a, and the outlet 17 b is mounted on one pointwhere refrigerant in the indoor heat exchanger 14 is in a saturatedstate, so that the temperature sensor 17 c can measure a temperature ata saturated state of the refrigerant.

The temperature at a saturated state is a temperature when there is notemperature change even if a phase of the refrigerant changes followingheat exchange of the refrigerant.

The controller has an ideal degree of superheat and an ideal degree ofsubcooling preset thereto at a pressure of the refrigerant, and anactual degree of superheat and an actual degree of subcooling arecalculated with temperatures measured at respective portions of theindoor heat exchanger 14 with the temperature sensors 17 a, 17 b, and 17c.

The degrees of superheat or subcooling is a temperature differencemeasured between the temperature sensor 17 b at the outlet and thetemperature sensor 17 c at the middle of the indoor heat exchanger 14.

The degree of superheat is a temperature difference at the time ofcooling, and the degree of subcooling is a temperature difference at thetime of heating.

A method for controlling a flow rate of refrigerant with reference tothe degree of superheat or subcooling in the air conditioning systemwill be described.

FIG. 3 illustrates a flow chart showing the steps of a method forcontrolling an air conditioning system in accordance with a preferredembodiment of the present invention.

Referring to FIG. 3, the method for controlling an air conditioningsystem includes the steps of setting an ideal degree of subcooling andan ideal degree of superheat at a controller (S1), measuring the degreeof subcooling or superheat of the refrigerant flowing in an indoor heatexchanger (S2), comparing the degree of subcooling or superheat set thusto the degree of subcooling or superheat measured (S3), and controllinga flow rate of the refrigerant flowing in the indoor heat exchangeraccording to a result in the step S3 in which the degree of subcoolingor superheat set thus is compared to the degree of subcooling orsuperheat measured.

As described, the degree of superheat or the degree of subcooling is adifference between a temperature of the refrigerant at the outlet of theindoor heat exchanger 14, and a temperature of the refrigerant at asaturation state of the refrigerant flowing in the indoor heat exchanger14.

Moreover, as described, the temperatures of the refrigerant are measuredwith a plurality of temperature sensors 17 a, 17 b, and 17 c mounted onthe indoor heat exchanger 14.

At first, a setting step (S1) is performed, in which an ideal degree ofsuperheat and an ideal degree of subcooling at the time of operation ofthe indoor heat exchanger are set at the controller. The ideal degree ofsuperheat and the ideal degree of subcooling vary with a pressure of therefrigerant and an environmental temperature.

Then, a measuring step (S2) is performed, in which an actual degree ofsuperheat or an actual degree of subcooling of the refrigerant flowingin the indoor heat exchanger 14 is measured. In the measuring step (S2),the temperatures of the refrigerant are measured with the temperaturesensors 17 a, 17 b, and 17 c mounted on the indoor heat exchanger 14.

That is, since the degree of superheat or the degree of subcooling is adifference of a temperature of the refrigerant at the outlet of theindoor heat exchanger 14 and a saturation temperature of the refrigerantflowing in the indoor heat exchanger, the controller can calculate thedegree of superheat or the degree of subcooling with the temperaturesmeasured at the temperature sensors 17 a, 17 b, and 17 c.

Then, a determination step (S3) is performed, in which a measured degreeof superheat or subcooling is compared to a preset degree of superheator subcooling. In the determination step (S3), it is determined whetherthe measured degree of superheat or subcooling converges to the presetdegree of superheat or subcooling, or not, or if not, which one has howmuch difference.

Then, an adjusting step (S4) is performed, in which a flow rate of therefrigerant flowing in the indoor heat exchanger 14 is adjustedaccording to a result of determination in the determination step (S3).

In the adjusting step (S4), the flow rate of the refrigerant is adjustedby controlling the flow rate control valve 13 a, and 13 b at oppositeends of the indoor heat exchange part 10.

In more detail, if the degree of superheat measured is higher than thepreset degree of superheat at the time of room cooling, opening of theflow rate control valves 13 a, and 13 b are adjusted, to increase a flowrate of the refrigerant flowing in the indoor heat exchanger 14 (S4 a),and if the degree of superheat measured is lower than the preset degreeof superheat at the time of room cooling, opening of the flow ratecontrol valves 13 a, and 13 b are adjusted, to decrease a flow rate ofthe refrigerant flowing in the indoor heat exchanger 14 (S4 c).

If the degree of superheat measured is the same with the preset degreeof superheat the time of room cooling, the flow rate of the refrigerantflowing in the indoor heat exchanger 14 is maintained (S(S4 b).

In the meantime, if the degree of subcooling measured is higher than thepreset degree of subcooling at the time of room heating, opening of theflow rate control valves 13 a, and 13 b are adjusted, to increase a flowrate of the refrigerant flowing in the indoor heat exchanger 14 (S4 a),and if the degree of subcooling measured is lower than the preset degreeof subcooling at the time of room cooling, opening of the flow ratecontrol valves 13 a, and 13 b are adjusted, to decrease a flow rate ofthe refrigerant flowing in the indoor heat exchanger 14 (S4 c).

If the degree of superheat measured is the same with the preset degreeof superheat the time of room cooling, the flow rate of the refrigerantflowing in the indoor heat exchanger 14 is maintained (S(S4 b).

The operation of the air conditioning system will be described.

FIGS. 4 and 5 illustrate graphs showing variations of a pressure ‘P’ andenthalpy ‘h’ of refrigerant at the outdoor heat exchange part 20 and theindoor heat exchange part 10 at the time of room cooling and roomheating of the air conditioning system, respectively.

The air conditioning system cools or heats the room depending on anoperation.

At the time of cooling or heating, the hybrid heat exchange part 30exchanges heat between the outdoor heat exchange part 20 and the indoorheat exchange part 10.

The cooling operation will be described with reference to FIGS. 1 and 2.

The refrigerant in the outdoor heat exchange part 20 is compressed atthe compressor 22, and forwarded to the flow controller 23 (A-Bsection). The flow controller 23 changes over the refrigerant to a sideof the fourth heat exchanger 24. In this instance, the refrigerantintroduced to the fourth heat exchanger 24 is condensed as therefrigerant heat exchanges with outdoor air (B-C section). The condensedrefrigerant changes to a refrigerant of a low temperature and lowpressure as the refrigerant passes through the expansion device 28 (C-Dsection). After cooling down the third heat exchanger 26 of the hybridheat exchange part 30, the low temperature and low pressure refrigerantis introduced into the compressor 22 through the flow controller 23 (D-Asection). In the outdoor heat exchange part 20, the compressor 22 servesas a driving source if the refrigerant flow.

Then, the refrigerant in the indoor heat exchange part 10 is cooled downas the second heat exchanger 16 and the third heat exchanger 26 in thehybrid heat exchange part 30 exchange heat (e-a section). Therefrigerant cooled down thus is pumped to a side of the first heatexchanger by the pump 12 (a-b section). In this instance, therefrigerant is neither in a two phase state, nor at a saturatedtemperature. The pumped refrigerant is introduced to the first heatexchanger 14 through the flow rate control valves 13 a, and 13 b at aninlet of the first heat exchanger 14, and discharged from the first heatexchanger 14 after heat exchanger with room air (b-c-d section).

The refrigerant in the indoor heat exchange part 10 reaches to asaturation temperature at which the refrigerant is involved notemperature change, but a phase change as the refrigerant heat exchangeswith room air (c point). In this step, the temperature sensor 17 cbetween opposite ends of the first heat exchanger 14 measures asaturation temperature of the refrigerant, and the temperature sensor 17b at the outlet of the first heat exchanger 14 (corresponding to ‘d’point) measures a superheated temperature of the refrigerant.

According to this, the controller determines a difference between thesaturation temperature and the superheated temperature, to derive thedegree of superheat, compares the derived degree of superheat to thepreset degree of superheat of the refrigerant, and adjusts opening ofthe flow rate control valves 13 a, and 13 b.

That is, if it is determined that the measured degree of superheat ishigher than the preset degree of superheat, opening of the flow ratecontrol valves 13 a, and 13 b on the first heat exchanger 14 is madegreater, to increase a flow rate of the refrigerant.

Opposite to this, if it is determined that the measured degree ofsuperheat is lower than the preset degree of superheat, opening of theflow rate control valves 13 a, and 13 b on the first heat exchanger 14is made smaller, to decrease a flow rate of the refrigerant.

In this instance, of the flow rate control valves 13 a, and 13 b onopposite ends of the first heat exchanger 14, though it is preferablethat opening of the flow rate control valve 13 a at an inlet end of thefirst heat exchanger 14 is made greater or smaller, and opening of theflow rate control valve 13 b at an outlet end of the first heatexchanger 14 is opened to the maximum, the way of opening of the flowrate control valves 13 a, and 13 b is not limited to this one.

According to this, the flow rate of the refrigerant to the first heatexchanger 14 can be controlled to the optimum.

After making heat exchange at the first heat exchanger 14, therefrigerant is discharged from the first heat exchanger 14 to the secondheat exchanger 16 of the hybrid heat exchange part 30, and cooledtherein again, to circulate therefrom.

Next, heating operation will be described with reference to FIGS. 1, 2,and 5.

After compressed at the compressor 22 in the outdoor heat exchange part20, the refrigerant is forwarded to the flow controller 23 (A-B). Theflow controller 23 changes over the refrigerant to a side of the thirdheat exchanger 26 of the hybrid heat exchange part 30. In this instance,the refrigerant introduced into the hybrid heat exchange part 30discharges heat, and condensed at the third heat exchanger 26 (B-C). Thecondensed refrigerant is changed to refrigerant of a low pressure and alow temperature as the refrigerant passes through the expansion device28 (C-D), introduced into the fourth heat exchanger 24, heat exchangeswith outdoor air, and is introduced into the compressor through the flowcontroller 23 (D-A). A circulation direction of the refrigerant in theoutdoor heat exchange part 20 is opposite to the cooling operation.

Then, the refrigerant at the indoor heat exchange part 10 has a pressureboosted by pumping of the pump 12 (a-b). The pumped refrigerant isheated as the refrigerant heat exchanges at the second heat exchanger 16of the hybrid heat exchange part 30 with the third heat exchanger 26 ofthe outdoor heat exchange part 20 (b-c).

The refrigerant heated thus is forwarded to a side of the first heatexchanger 14 by the pump 12. The refrigerant introduced into the firstheat exchanger 14 heat exchanges with room air to heat the room, whilethe refrigerant itself is condensed (c-a).

In this instance, as the refrigerant in the first heat exchanger 14 heatexchanges with the room air, the refrigerant reaches to a saturationtemperature at which the refrigerant is involved in no temperaturechange, but a phase change (d-e). In such a step, the temperature sensor17 c between the refrigerant inlet/outlet of the first heat exchanger 14measures the saturation temperature of the refrigerant (‘e’ point), andthe temperature sensor 17 b at the outlet of the first heat exchanger 14measures a superheated temperature of the refrigerant (‘a’ point).

According to this, the controller derives the degree of superheat as adifference between the saturation temperature and the superheatedtemperature, compares the derived degree of superheat to the presetdegree of superheat of the refrigerant, and adjusts opening of the flowrate control valves 13 a, and 13 b.

That is, if it is determined that the measured degree of superheat ishigher than the preset degree of superheat, opening of the flow ratecontrol valves 13 a on the refrigerant inlet of the first heat exchanger14 is made greater, to increase the flow rate of the refrigerant to thefirst heat exchanger 14.

Opposite to this, if it is determined that the measured degree ofsuperheat is lower than the preset degree of superheat, opening of theflow rate control valves 13 a is made smaller, to decrease a flow rateof the refrigerant. According to this, the flow rate to the first heatexchanger 14 is adjusted.

The refrigerant having room air heat exchanged therewith at the firstheat exchanger 14 makes circulation in which the refrigerant isintroduced into, and heated again at the second heat exchanger 16 of thehybrid heat exchange part 30.

As has been described, the air conditioning system and the method forcontrolling the same of the present invention have the followingadvantages.

The supply of refrigerant to the indoor heat exchange part by using apump as a driving source that requires no oil permits to dispense withan oil recovery operation at the indoor heat exchange part.

According to this, the air conditioning system can be installed on amultistory building without limitation of a height of the building asfar as a capacity of the pump permits. Moreover, even if a refrigerantpipe is long, the air conditioning system is applicable even to a systemwith a refrigerant pipe line longer than the related art as far as thecapacity of the pump permits.

Moreover, the compressor and the expansion device of the outdoor heatexchange part may be placed outside of a room mounted on the outdoorunit. Therefore, even if the compressor and the expansion devicegenerate noise, the noise can not reach to the user.

Furthermore, since the outdoor heat exchange part is connected to theindoor heat exchange part through the hybrid heat exchange part, alength of the refrigerant pipeline of the outdoor heat exchange part canbe shortened significantly regardless of a height of the building.According to this, a refrigerant recovery ratio can be improvedsignificantly, to prevent the compressor suffering from damage caused bya poor refrigerant recovery ratio.

Since the saturation temperature of the refrigerant can be measured atthe first heat exchanger in the indoor heat exchange part, control ofthe refrigerant flow rate to the first heat exchanger can be optimized.

The optimum control of the refrigerant flow rate from the first heatexchanger permits fine control of the room temperature.

The no provision of the compressor and the expansion device to theindoor heat exchange part to be installed in a room permits simplestructure of the indoor heat exchange part, which enables to reduceprice of the indoor unit.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An air conditioning system comprising: an outdoor heat exchange partincluding a compressor for compressing refrigerant, an outdoor heatexchanger for making the refrigerant to heat exchange with outdoor air,and an expansion device for expanding the refrigerant; an indoor heatexchange part including a pump for making refrigerant in a flow pathindependent from the outdoor heat exchange part to flow, an indoor heatexchanger for making the refrigerant heat exchange with room air, and aflow rate control device for controlling a flow rate of the refrigerant;and a hybrid heat exchange part for making the outdoor heat exchangepart and the indoor heat exchange part, which are independent from eachother, to heat exchange with each other.
 2. The system as claimed inclaim 1, wherein the flow rate control device includes; a temperaturesensor for measuring temperatures of refrigerant flowing in the indoorheat exchanger, a controller for determining a degree of superheat orsubcooling of the refrigerant with the temperatures measured at thetemperature sensors, and a flow rate control valve for controlling arefrigerant flow rate to the indoor heat exchanger according to thedetermination of the controller.
 3. The system as claimed in claim 2,wherein the flow rate control valve is mounted on a refrigerant inletend of the indoor heat exchanger.
 4. The system as claimed in claim 2,wherein the flow rate control valve is mounted on a refrigerant outletend of the indoor heat exchanger.
 5. The system as claimed in claim 2,wherein the temperature sensors are mounted on the refrigerant inletend, the refrigerant outlet end, and a predetermined portion between therefrigerant inlet end and the refrigerant outlet end of the indoor heatexchanger.
 6. The system as claimed in claim 5, wherein thepredetermined portion between the refrigerant inlet end and therefrigerant outlet end of the indoor heat exchanger is a section inwhich the refrigerant flowing in the indoor heat exchanger is in asaturated state.
 7. A method for controlling an air conditioning systemcomprising the steps of: setting an ideal degree of superheat, and anideal degree of subcooling at a controller; comparing the degree ofsuperheat or subcooling set thus with a degree of superheat orsubcooling measured thus; and controlling a flow rate of refrigerantflowing in an indoor heat exchanger according to a result of the step ofcomparing the degree of superheat or subcooling set thus with a degreeof superheat or subcooling measured thus.
 8. The method as claimed inclaim 7, wherein the degree of superheat or subcooling is a differencebetween a temperature of the refrigerant at the refrigerant outlet ofthe indoor heat exchanger and a saturation temperature of therefrigerant flowing in the indoor heat exchanger.
 9. The method asclaimed in claim 7, wherein the step of controlling a flow rate ofrefrigerant flowing in an indoor heat exchanger includes the steps of;increasing the flow rate of the refrigerant flowing in the indoor heatexchanger if the degree of superheat measured is higher than the degreeof superheat set, and decreasing the flow rate of the refrigerantflowing in the indoor heat exchanger if the degree of superheat measuredis lower than the degree of superheat set.
 10. The method as claimed inclaim 7, wherein the step of controlling a flow rate of refrigerantflowing in an indoor heat exchanger includes the steps of; increasingthe flow rate of the refrigerant flowing in the indoor heat exchanger ifthe degree of subcooling measured is higher than the degree ofsubcooling set, and decreasing the flow rate of the refrigerant flowingin the indoor heat exchanger if the degree of subcooling measured islower than the degree of subcooling set.
 11. An air conditioning systemcomprising: at least one first heat exchanger for heat exchange withroom air; a second heat exchanger for transferring heat from the firstheat exchanger to an outside of a refrigerant flow path having the firstheat exchanger mounted therein; a pump for circulating the refrigerantto the first heat exchanger and the second heat exchanger; a third heatexchanger in a flow path independent both from the first heat exchangerand the second heat exchanger for heat exchange with the second heatexchanger; a fourth heat exchanger for transferring heat from the thirdheat exchanger to outdoor air; a compressor for compressing therefrigerant and circulating the refrigerant to the third heat exchangerand the fourth heat exchanger; a plurality of temperature sensors formeasuring temperatures of the refrigerant flowing in the first heatexchanger; and at least one flow rate control valve for controlling aflow rate of the refrigerant flowing in the first heat exchangeraccording to temperatures measured at the temperature sensors.
 12. Thesystem as claimed in claim 11, wherein the temperature sensors areprovided at a refrigerant inlet end and a refrigerant outlet end of thefirst heat exchanger, and at a predetermined portion between therefrigerant inlet end and the refrigerant outlet end, respectively. 13.The system as claimed in claim 11, wherein the temperature sensorprovided at a predetermined portion between the refrigerant inlet endand the refrigerant outlet end measures a saturation temperature of therefrigerant flowing in the first heat exchanger.
 14. The system asclaimed in claim 11, wherein the flow rate control valves are providedto a refrigerant inlet end and a refrigerant outlet end of the indoorheat exchanger.
 15. The system as claimed in claim 14, wherein, at thetime of controlling a refrigerant flow rate, an opening of the flow ratecontrol valve at the refrigerant inlet end of the first heat exchangeris adjusted, and an opening of the flow rate control valve at therefrigerant outlet end is opened to the maximum.